Conventionally, since aliphatic polyamides, such as polyamide 11 and polyamide 12, are excellent in terms of chemical resistance, these polyamides have been widely used as materials for various types of films and hollow molded bodies, such as a hose, a tube, and a pipe, which have been used for fuel transportation, fuel storage or the like. Films and hollow molded bodies used for these intended uses are required to have high gas barrier properties, in order to suppress permeation of volatile components such as volatile hydrocarbon through these films or hollow molded bodies, and diffusion thereof in the air.
However, although molded bodies formed from aliphatic polyamides, and in particular, from polyamide 11 or polyamide 12, are excellent in terms of toughness, chemical resistance and flexibility, they do not have sufficient barrier properties against various types of gases such as oxygen and volatile hydrocarbon. Accordingly, it has been desired to improve the gas barrier properties of them.
As a means for enhancing the gas barrier properties of a molded body, a method of blending a semi-aromatic polyamide in addition to polyamide 11 or polyamide 12 has been proposed (Patent Literature 1: JP Patent Publication (Kokai) No. 2008-133455 A). However, this method has been problematic in that flexibility becomes insufficient, depending on the amount of a semi-aromatic polyamide added.